Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 261007 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 610 AM EDT Mon Sep 26 2016 .SYNOPSIS... A stalled front will waver across the area today. A stronger cold front will approach Wednesday before slowly crossing the area through late in the week although timing of this front is highly uncertain. Cooler and drier weather is expected by the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM Monday...Progressive flow aloft and at the sfc this period as witnessed by all models which are in general in good agreement for this period. The eastward moving mid- level ridge axis pushes overhead today...and east of the FA tonight. Some bagginess or weak troffiness upstairs, underneath this ridge, has lagged behind across the SE U.S. States this past weekend and into this period. A mid-level trof closes off across the western Great Lakes by late today, and further deepens as it drops to the Central Great Lakes by daybreak Tue. In essence, the U.S. east of the Mississippi River is now under the influence of this upper closed low. Not quite a cut-off due to the upper westerlies are still pushing thru this upper feature. Model are in good agreement with movement of sfc features this period. A 1025mb centered sfc high over New England this morning, will ridge across the Carolinas into Ga today. The center of this high pushes off the New England coast and drops SSE to the offshore waters from the Mid-atlantic states tonight but still continues to ridge back across the previously mentioned states. An inverted sfc trof develops just offshore and parallel to the ILM CWA coastline tonight. And by Tue daybreak, a cold front associated with the expansive closed low, dropping SE and reaching the western Carolinas late tonight. Initially, the ILM CWA will have to deal with the bkn-ovc stratus deck at 2k to 3k feet this morning. This deck will become sct-bkn later today and tonight. As for POPs today, with little or no progged instability until late tonight, have decided to keep POPs out of the forecast for daylight Mon. This shown by the latest RAP and HRRR models. For tonight, will indicate a slow increase in POPs as the inverted trof offshore develops, along with a weak sfc low off SC/GA coasts from the dynamics associated with the bagginess aloft discussed earlier. POPs from this feature and also increasing POPs from the approaching cold front will be advertised across the FA. Via latest RH model time height displays across the FA, plenty of mid and upper level dry air today will mix with the lower levels and partially scour out some of this low level stratus. Thus, have stayed close to a consensus for the max/min temp model mos guidance...with an emphasis of slightly hier, by 1 to 2 degrees, for todays highs. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 400 AM Monday...Amazingly, the models have the general idea of a closed low dropping south from the Great Lakes and becoming a cutoff low by the end of this period, with the westerlies bypassing this upper low by the end of this period. Like spokes on a bicycle, weak mid-level vorts or S/w trofs, rotating around the upper low, will occasionally affect the FA this period. More-so when this upper low drops to the central Appalachians. These s/w`s will be able to interact with dynamics from the slow moving sfc cold front moving/slithering across the FA. POPs will be advertised each day, likely hiest during Tue due to the passage of the sfc low along the inverted sfc trof just off the coast. With the cold pool aloft partially reaching the area during the latter half of this period, increasing the lapse rates and instability, especially involving the days insolation, the chance for thunderstorms will exist thruout this period. Leaned toward the European MOS Guidance over the GFS Mos due to its recent slightly better performance over the GFS Mos. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 300 AM Monday...Big differences in the extended continue to cause lowered confidence for late this week. While the guidance all shows a deep trough closing off across the OH VLY, the evolution thereafter becomes quite muddled. The ECM continues to be a strong/slow/west outlier with this feature as it digs into the lower Appalachians and then actually retrogrades to the NW through Saturday before finally ejecting late in the wknd. The GFS/CMC are more in line with a sharp digging through Thursday and then lifting off to the NE through New England Friday and into the wknd. Although the ECM has been consistent the last few days, the GFS solution is still preferred as a retrograde west of the upper low into a +3 SD ridge seems unlikely. WPC cannot rule out any solution at this time however, so a blended forecast is preferred with highest weight on the GFS. This upper low will determine the passage of a surface cold front which continues to slow in forecast guidance. Favoring the GFS, FROPA is now expected early Thursday, with cool and dry weather expected Fri-Sun. In fact, temps Fri-Sun may fall slightly below climo for both highs and lows as the first fall-like airmass of the season advects into the Carolinas beneath Canadian high pressure. Will note that if the ECM solution verifies, the front won`t cross until Saturday, leaving much more unsettled weather through the week, along with continued above normal temperatures. && .AVIATION /12Z MONDAY THROUGH FRIDAY/...
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As of 12Z...A washed out front will remain nearly stationary and dissipate today. Predominately easterly flow, a bit more northeasterly early on. There will be quite a bit of a high stratocu deck this morning, more scattered by this afternoon. Tonight some fog entering the picture well after midnight, mainly inland. EXTENDED OUTLOOK...Chance for SHRA/TSRA each day through Wednesday, with morning fog/stratus also possible. VFR Thursday and Friday.
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&& .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 330 AM Monday...Small craft exercise caution thresholds will be flirted with today, mainly across the waters from Cape Fear northward. Sfc ridging to persist across the local area, extending from the highs 1025 mb center, in transit from New England to offshore from the Mid-Atlantic states by Tue daybreak. By Tue morning, models indicate an inverted sfc trof parallel and offshore from the Carolina coasts. In all, this means a continued onshore wind trajectory and with a semi-tightened sfc pg, wind speeds will run around 15 kt with possible gusts up to 20 kt today, dropping to 10-15 kt tonight. Significant seas will run 2 to 4 ft thru tonight, except a solid 3 to 4 ft north of Cape Fear and also south of Murrells Inlet. Both locations away from the influence of Frying pan Shoals. Wind waves at 4 to 6 periods will dominate with an underlying 1 to 2 foot ese ground swell at 9 to 10 second periods. SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 400 AM Monday...Will see a veering trend to the winds from easterly at the start of this period, to south southwest by the end of this period. Weak sfc low to move along the inverted sfc trof Tue. The sfc cold front to drop SE at a snail`s pace this period, reaching the local waters by Thu morning. Wind speeds may become temporarily northerly up to 15 kt after the low passes by early wed, otherwise looking at around 10 kt for speeds with the sfc pg relaxing up until the sfc cold front reaches the coast. Significant seas will run 2 to 3 ft, possibly and briefly up to 4 ft at the start of this period due to the passage of the sfc low. Wind driven waves to dominate thru early Wed with periods running 4 to 6 seconds. ESE, 1 to 2 foot ground swell at 9 second periods will become dominate later Wed into early Thu. LONG TERM/THURSDAY THROUGH FRIDAY/... As of 300 AM Monday...Still some uncertainty in the extended with respect to a frontal passage, but attm expect FROPA to occur Thursday with W/SW winds around 10 kts becoming NW late. High pressure will build in behind this front creating a very weak pressure gradient, so winds across the waters on Friday will feature highly variable direction with speeds of 5-10 kts. Seas of 2-3 ft Thursday will fall to around 2 ft on Friday thanks to the weaker winds, and a continuing 2ft/9-10 sec SE swell. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DCH SHORT TERM...DCH LONG TERM...JDW AVIATION...43 MARINE...DCH

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